Sulphate acidic soils in coastal areas of Lower Saxony 1 : 50 000 - below 2 m depth

Description

This map shows the risk of spreading potentially sulphate acidic soils below 2 m depth to the base of the Holocene sediments. Important: This map, unlike the 0-2 m depth map, has not been reworked in 2018, but the same new legends are used here as well. The explanatory geofacts 24 are currently under revision. There are no values for this map east of Cuxhaven and Bremerhaven, as their data base, the geological coastal map of Lower Saxony, also ends there. So-called ‘sulphate acid soils’ occur in Lower Saxony mainly in the area of coastal areas. This term includes soils as well as lower-lying sediments and peat. Characteristic for the various sulfate acid materials (SSM) are high, geogen-related contents of reduced inorganic sulfur compounds. Originally, sulphur in the form of sulphations from seawater entered the Holocene deposits. Due to water-saturated, anaerobic conditions, the sulphations were reduced to sulphide and preserved for a long time mainly as pyrite and FeS due to consistently high groundwater levels. Typical SSMs are clay-rich materials with higher levels of organic matter and/or coarse plant residues as well as over- and through-sludged low-moor peat. The dewatering and aeration of these materials leads to the oxidation of the sulfides and the formation of sulphuric acid, e.g. when they are dewatered in the context of construction projects or removed from the natural compound. Potentially sulphate acidic soils can thus currently become sulphate acidic soils. The high risk potential results from: extreme Versauerung (pH < 4,0) des Baggergutes mit der Folge von Pflanzenschäden, deutlich erhöhte Sulfatkonzentrationen im Bodenwasser bzw. Sickerwasser, erhöhte Schwermetallverfügbarkeit bzw. -löslichkeit und erhöhte Konzentrationen im Sickerwasser; hohe Korrosionsgefahr für Beton- und Stahlkonstruktionen. In order to prevent or minimise danger, all construction measures involving excavated soil or groundwater subsidence in the affected areas require in-depth technical planning and monitoring. It should be noted that the distribution of iron sulfides in the area and depth is often rather spotty. Therefore, the identification of current and potential SSM as well as construction planning and supervision should only be carried out by qualified soil science specialists. Due to the often low load-bearing capacity of these soils and in particular the peat, relatively large excavation pits must be excavated during construction measures, so that in a short time a lot of SSM is generated as excavated material. In addition, oxidation and acidification often take place very quickly. This evaluation map can already be used in the planning and designation of areas, e.g. in the context of route planning, land use and development plans, etc. Specific instructions on construction planning and supervision as well as on sampling and laboratory analysis of the SSM to be relocated can be found in Geofakten 25. Attention: The map is only the basis for a concrete exploration at the site of the construction project.

Resources

Name Format Description Link
0 https://nibis.lbeg.de/net3/public/ogc.ashx?NodeId=580&Service=WMS&Request=GetCapabilities&

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